1. Field of the Invention
The present invention relates to an optical communication network, and more particularly, to an optical communication network including an Optical Line Terminal (OLT), and at least one Optical Network Terminal (ONT) accessing the OLT.
2. Description of the Related Art
Countries the world over are making every effort to reduce a green-house gas production and energy consumption in order to alleviate climate change. The information technology (IT)_fields are no exception, and various green IT technologies are being discussed at standardization organizations. In particular, in network fields, power consumption of subscriber networks accounts for 80% of the entire network power consumption. Most of all, considering that power consumption of an Optical Network Terminal (ONT) that is used in every home accounts for 60% of the entire network power consumption, a power reduction technique for the ONT in the optical subscriber network has a great ripple effect.
Among various optical subscriber network technologies, Gigabit Passive Optical Network (GPON) and 10-Gigabit Passive Optical Network (XGPON) are next generation optical subscriber network technologies. The GPON and XGPON technologies have been standardized by the International Telecommunications Union-Telecommunication Standardization Sector (ITU-T), and commercially serviced rapidly in North America and Europe. These technologies have an advantage in that an increase in interoperability and a simple operability management are possible using an ONT Management Control Interface (OMCI) which has a strong control and management function.
The ITU-T recognizes a necessity for power reduction in the next generation optical subscriber network, and publishes a White Paper regarding a power reduction technique, as a guideline for future standardization tasks. The power reduction technique which has been discussed as standards based on the White Paper provides two types of modes, that is, a dozing mode and a cyclic sleep mode. The dozing mode is a method of periodically powering a transmission unit of the ONT on/off, in a state where a reception unit of the ONT is constantly powered on, which has an advantage in that a stable operation may be possible despite low efficiency in power reduction. The cyclic sleep mode is a method of periodically powering both the transmission unit and the reception unit of the ONT on/off, which has a disadvantage in that a loss of traffic which is input when the reception unit is powered off may occur, however, has an advantage in that efficiency of the power consumption may be improved.